Switch blade



Sept. 27, 1932. I A KEMPTQN 1,8519303 SWITCH BLADE Filed Oct. 30, 1929InVenov-I Les|iev \.Kernpcc-n b5 His Attornegl ranges.

o practice that arcing Patented Sept. 27, 1932 UNITED s'rArss "PATENTOFFICE mean: a. xmrr'ron,

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Application am October so, me. lerhl no. team.

The present invention relates to blades for sna switches and especiallyto switchesinten ed for controlling the circuits of electric heatingdevices, as for example electric Such switch blades have to carry largeamounts of current and are frequen y operated. Although means. areprovided for actuating the movable member or blade with a snap action,it is found in takes place when the cirrelativel contacts and movableblades. For example, the structure shown in my Patent 1,670,07 3 grantedMay 15, 1928 may be used.

5 indicates a four arm switch blade or spring contact brush, two of saidarms being lon er than the others so as to engage a di erent set ofstationary contacts, one pair of arms extending at ri ht angles to theother pair. They are ma e of good spring material, such as phosphorbronzeor equivcuit is 0 ed WlllCh causes burning or pitalent metal. Theyare assembled in the ting of t e surfaces thereof. When the surswitch inpairs as shown in Fig. 2, and as faces become rou hened in this .mannerthe contact between 51c moving and stationary parts is impaired, whichin turn causes local heating of the arts which is ob'ectionable as willreadily appreciated. 11 order to improve the operation it We standardpractice to coat the contacting surfaces with some kind of grease orheavy oil which while it makes the parts move easily has the effect, escially where an excess of (grease is used, 0 increasing the trouble incient to arcing. My invention has for its object to improve theconstruction of switch members or blades or both by providingembossments thereon to the end that the arcing or burning is confined toportions of the surfaces or parts of the members or blades other than atthe embossments through which the current flows when the switch isclosed.

Fora consideration of what I believe to be novel and my invention,attention is directed to the accom anying description and the claimsappende thereto. I

In the accompanying drawing, which is illustrative of my invention, Fig.1 is a plan view of a rotatable switch blade, Fig. 2 is an edge viewshowin how the parts are arranged in a switch, ig. 3 is an end view ofone of .the blade arms, and Fig. 4- is a sectional view on an enlargedscale of a pair of moving blades and a stationary contact;

In order to simplify the descr1 tion of my invention, the details of theswitc operating mechanism as Well as some of the other parts have beenomitted. It is to be understood, however, that in this particular ansuitable operating mechanism may be emp oyed and practice, each manypairs may be provided as are necessary for controlling the circuits ofthe heating or other devices associated with the switch.

The blades or brushes are so made and assembled as to be biased towardeach other so as to make good contact with the'stationary contacts. 6indicates stationary contacts which are bridged by the blades to closethe circuit between them.

Instead of makin the contact surfaces at the ends perfectly at andsmooth and flush with the body of the blade as is the standard isprovided with a shallow embossment 7 which rises slightly above themetal forming the other part. he embossments are formed b suitable dies,and their surface area should great enough to carry 'the current withoutappreciable local heatin The amount that each embossment is raised willdepend chiefly upon the thickness of the stationary contact and on theshape or curvature of the edges of the blades. For example, and 36amperes, as shown, the embossment may be raised by an amount of the,order. of to 0ne-quarter of the thickness/of the blade. The object isto raise it aslittle as possible and yet provide a surface 'which willremain smooth and free from burning due to arcing when the circuit isbroken. The end portions of each blade arm are bent or curved away fromthe plane of the blade to a lower level as indicated at 8 startin at ornear the base of the embossment so that all danger of the parts 'ammingwhen the blade is moved is obviated, and to cause whatever arc is formedto be beyond the embossment.

in switches designed for 225 volts any suitable arrangement of thestationary The amount that the ends are bent or curved will dependchiefly u on the thickness of the stationary contacts. he oint is theyshould afiord an easy entrance or the contact between the blades as wellas form arcing surfaces below the level of the embossment.

The entering edges of the stationary-contacts'are-beveled or sharpenedas shown at 9 in Fig. 4. As the air of moving blades is rotated by asuitab e means (not snown) to interrupt the circuit, the embossmentspass out of en agement with the stationaryicontact and due to the springof the blade arms they move toward each other, still graspmg the contactbetween them but'in regions beyond the embossments. This has the efiectof causing the arcing to take place not at or on the embossments but mare on or regions outside thereof, for examp e as at 10 and 11, the arefollowing the metal outward from the embossments until broken by relaftive movements of the stationary and moving parts. To state the matterin other words,

I the embossments ride on the stationary contact,then move toward eachother while other parts ofthe blade maintain the electric circuit andthe arc is finallylbroken at the level or region belowlandbeyond theembossments. As a preferred arrangement, I have shown a pair of bladesengaging op osite sides of the same stationary contact at where thecurrents to be carried are small a single blade may be employed, havingof course, the embossment arranged in the manner described.

In this case the arc will be obliged to follow one path instead of two.

Tests made with switches embodiyrng my improved blade show substantialmprovement over the prior smooth or non-embossment type in the absenceof roughenlng, pitting and local heating. For example, switches fittedwith my improvement have been given a rotary test of 12,000 cycleswithout any trouble from flashin or burning, and the embossmentsremained smooth and clean, such roughening and pitting as took placebeing wholly outside the embossments. In the particular test referredto, the voltage was 255 and the current 36 amperes. In one test theswitch was placed in circuit with a high heat coil of a range on a 112volt circult with a current of 48 amperes, and after 144 hours ofoperation had a temperature of 125 F., with a room temperature of 92 F.,or a rise of only 33 F. over room temperature, which is substantiallyless than is normally the case. Due to the fact that the contactingsurfaces remain smooth, the local heatin of the switch at the contactsas'indicated a bove is small, and the life of the switch is therebyincreased.

What I claim asnew and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, a pair of'sheet metal switch blades, each of whichhas a shallow embossment pressed therefrom to form a fiat ammo:

contact surface of considerable area which rises above the level of thesurrounding part of the blade, said embossments facing each other, witha stationary contact adapted to be engaged on opposite sidessuccessively by the embossments and the surrounding parts of the bladesas the blades move out of enga'gement with the stationa contact.

2. In combination, a rigi contact and a spring contact brush adapted toe age said rigid contact and having an er iliossment forming a contactsurface and an adjacent surface adapted to engage the ri 'd contact asthe contact brush is separate from said rigid contact to open anelectric circuit, and provide an arcingsurface for said contact rus 3.In combination, a rigid contact and spring contact brushes adapted toengage said rigid contact and having embossments forming contactsurfaces and surfaces adjacent said contact surfaces adapted to engagethe rigid contact as the contact brushes se arate from said rigidcontact to open an e ectric circuit, and rovide arcing surfaces for saidcontact bruslies. I

4. In combination, a rigid contact and two spring contact brushesadapted to engage said rigid contact and having embossments formingcontact surfaces engaging opposite sides 0 said rigid contact andsurfaces adjacent said contact surfaces adapted to en gage the rigidcontact as the contact brushes separate from said rigid contact to openan electric circuit, and rovide arcing surfaces for said contactbrushes.

5. Aswitch member comprising twos ring contact brushes having em entsorming contact surfaces on the inner sides of the brushes and surfacesadjacent to the embossments forming arcing surfaces which are adapted toengage a contact after the em bossments have passed out of engagementwith the contact whereby the arcing of the contact brushes is limited toan area which is not in normal engagement with the contact when anelectric current is passing therethrou h.

6. switch member com rising two rin contact brushes biased towfrd eachothz r an having shallow embossments on the inner side of the contactbrushes forming flat contact surfaces raised above the adjacent surfaceof the contact brush whereby the surfaces adjacent to the embossmentsengage a contact. as the electric circuit is opened through the switchmember to prevent the

